COMPARISON BETWEEN EXPERIMENTS AND NUMERICAL CALCULATIONS ON S = 1/2 HEISENBERG-XY FERROMAGNETIC CHAINS K. Kopinga, J. Emmen, G. C. de Vries, L. F. Lemmens and G. Kamieniarz J. Phys. Colloques, 49 C8 (1988) C8-1451-C8-1452 DOI: 10.1051/jphyscol:19888666